Dasyatis colarensisZBKn. sp. is distinguished by the combination of the following characters: a diamond-shaped (rhomboid) disc and an elongate snout (preorbital distance ranging from 35.7 to 37.7 % in DW); presence of a dark and well defined band outlining the lower lips; row of small tubercles along midline of disc from shoulder region to base of tail, tubercles somewhat randomly distributed; posterior margins of pectoral fins uniformly rounded; triangular-shaped pelvic fins with posterior margin almost straight or slightly sinuous, pelvic fin tips exceeding posterior margins of disc; dorsal caudal keel absent in the holotype, but vestigial in both paratypes.

Description

Proportional dimensions as percentages of DW and meristic data are given respectively in tables I and II.

Corners of nasal curtain rounded; nasal curtain with fringed posterior margin and with a median hiatus. Mouth arched, with a straight and dark band outlining the lower lips. Median portion of lower jaw (symphysial region) slightly concave. Teeth in a pavement pattern; cusps pointed and curved backwards in the holotype. Subadult specimen with teeth near symphysis almost pointed. Dental formulae: 43-45/45-60. Three to four papillae in transverse series on mouth floor. In the holotype, the central papilla is curved forward, the two lateral ones show a singular bifurcated tip (paratypes have no bifurcated papillae). Gill slit apertures sinuous.

Pelvic fins triangular, with posterior margin almost straight or slightly sinuous. Tip of pelvic fin sharp, exceeding the limits of the posterior margin of disc. Well developed claspers in the holotype (with residual traces of sperm at the moment of capture). Medial margin of clasper groove slightly serrated at the glans. Tail (which seems complete) more than twice disc width (209.6 to 296.3%). Dorsal caudal keel absent in holotype but present in both paratypes as a low vestigial keel. Ventral finfold not high, its maximum height less than one third of caudal diameter at sting level (from 22.2 to 28.5%).

Central upper surface of disc covered with small, widespread, and flattened tubercles in a band along midline from level of orbits to base of tail. Tubercles also on rostral, preorbital and interorbital regions. Margin of disc naked. Dorsal thorn counts: 6 to 9 nuchals, 1 to 2 scapulars, 2 to 3 suprascapulars on the left side and 1 to 3 on the right, 12 to 17 median dorsals, and 6 to 9 median caudals. Ventral finfold, pelvic fins, claspers and ventral surface of the disc smooth. Sting missing in holotype (probably removed, original groove present). Counts of lateral sting barbs: 42 (left) and 48 (right) in juvenile paratype, 69 (left) and 70 (right) in subadult specimen.

Coloration in life very similar to that in preservative. Dorsal surface of the disc light brown; ventral surface whitish-gray with margins of pectoral fins and posterior margins of pelvic fins darker. Anterior margin of pelvic fin whitish to yellowish. Claspers and caudal ventral finfold dark brown.

Etymology

The specific name was selected for the geographic location of holotype, from the proximities of Colares Island, district of Colares ( Pará State, Brazil).

The shape of the disc, which is laterally rounded, promptly differentiates D. sabina from D. colarensisZBK , which has angular pectoral fin edges. In D. sabina the horizontal eye diameter is more developed (53% to 88% of spiracle length), whereas in D. colarensisZBK this proportion is 35.5 to 47.0 %. In D. sabina the upper surface of tail has a definite and high finfold, and the ventral finfold is larger than the caudal height. In D. colarensisZBK the dorsal finfold is absent (holotype) or vestigial (paratypes) and the height of the ventral finfold does not reach one-half of tail. The snout of D. sabina is shorter than in D. colarensisZBK ; horizontal eye diameter is 5.6 to 6.9% of preoral length in D. colarensisZBK , and the preoral length is 34.8 to 36.7 % of DW. In D. sabina these percentages are, respectively, 14% to 22% and 27. 7 % to 26.4%.

Dasyatis geijskesiZBK differs from D. colarensisZBK in possessing a very long preorbital snout length (40 to 50% of DW vs. 35.7 to 37.7% in D. coloarensisZBK ), very long prenasal snout length (37 to 45% of DW vs. 29.5 to 32.7%), very broad pelvic fins (38 to 42.9% of DW vs. 19.6 to 23.3%), and narrow pelvic fin base length (79.3 to 91.1% of internasal length vs. 119.2 to 124.2%).

With respect to DasyatisZBK from other regions, D. colarensisZBK resembles D. zugei ( Mueller & Henle, 1841) from China, Pakistan, Indonesia and the Sea of Japan, D. navarrae (Steindachner, 1892) and D. bennetti ( Mueller & Henle, 1841) from southeast Asia, and D. acutirostra (Nishida and Nakaya, 1988)ZBK from the Sea of Japan and the East China Sea, in having an elongated snout which reaches more than 25% of disc length (Chen, 1948; Chu & Wen, 1982; Monkolprasit, 1984; Nishida & Nakaya, 1990).

The pale-edged stingray D. zugei and the blackish stingray D. navarrae differ from D. colarensisZBK by presenting a well developed upper finfold in the former, and vestigial or absent finfold in the latter.

The smalltooth stingray D. rudis possesses the entire dorsal surface of disc rough with minute and dense asperities and no middorsal row of spines ( D. colarensisZBK presents small tubercles only at disc centre and a middorsal row of spines).

The sharpnose stingray D. acutirostraZBK presents a ventral finfold length ranging from 15.0% to 22.9% of DW (37.3 to 51.5% in D. colarensisZBK ), a preoral length ranging from 37.9% to 44.2% of DW (34.8 to 36.7% in D. colarensisZBK ), lacks a dorsal patch of tubercles and suprascapular thorns (both present in D. colarensisZBK ), and lacks oral papillae (three to four well developed papillae in D. colarensisZBK ).